Take both.
There, problem solved!
Seriously, I would, if space in your travel cases isn't an issue. Ditto lots of film, much cheaper anywhere else than in Japan. Add two UVs, two lens hoods. That's it. Oh, and heaps and heaps of film. In 2012, I shot Portra, but if I ever return to the enchanted, magical, mystical, wonderful place that is Kyoto, I'll take Fuji Velvia.
But then those beautiful Kyoto autumn landscapes just cry out for wide angle shots.
If time allows before you fly out, you can consider trading your two GAs for a GA645wi, which will give you 16 images to a 120 roll, and has two shutter buttons. handy for those long vertical shots of lovely maples in multicolors. I've owned two GAi models (sadly both deceased) in my time, and if I were to ever buy another one, it will be the 645wi.
Or toss a coin, and let how it falls decide which camera you'll take. Heads, the 645zi. tails, the 645i.
Gosh, these First World Problems we have... (black humor alert

)
If you can find it, buy, beg or borrow one of the excellent books by Tuttle (US publishers) on the gardens of Kyoto. I did in 2012 when we went to Japan to see the fall colors. It will be your ideal guide to a unique experience.
And 良い旅 to you both.
PS I took two Rolleifex Ts with 16 exposure kits to Kyoto in 2012. Any camera will do. The subject is everything!